GPT-5.6 Luna vs GPT-5.6 Terra for travel planning
Effectively a dead heat: 93–91
Same 12 travel planning tasks, marked blind by three rival labs. GPT-5.6 Luna took 2 tasks, GPT-5.6 Terra took 0, 10 tied. Tested 16 Aug 2026.
Where they differed most
Plan the SHAPE of a holiday from these constraints, all real: family of five — two parents, kids 9 and 6, and gran who cannot walk more than ten minutes; £1,600 all-in for a week in August; flying from Manchester only; dad burns easily and hates 'just sitting on a beach'; the 9-year-old is obsessed with castles. Offer 2 distinct holiday shapes (types of place and trip, not named resorts), what each one trades away, and the single constraint you would challenge first because it costs the most.
£1,600 for five people for seven nights in August is extremely tight once flights, bags, transfers, food, insurance and accessible transport are included. I would shape the trip around **one base, very little changing hotels, and pre-booked transport**. ## Shape 1: Flat historic-city base with one major castle day **Type of place:** A compact, relatively cool northern or central European city with a lift-equipped apartment near a tram or taxi rank, plus a famous castle or fortress reachable by train, taxi or an organised excursion. **How the…
At **£1,600 total for five in August from Manchester**, the holiday needs to be short-haul, apartment-based and built around **self-catering, public transport/taxis or a modest hire car** rather than a traditional package. Gran’s mobility also means “close to everything” matters more than having a huge resort. ## 1. A compact historic city with a castle focus, plus easy day trips **Shape:** Fly to an affordable Central/Eastern European city with a major castle/fortress and stay seven nights in an aparthotel or apartment within a very short t…
Task by task
| Task | GPT-5.6 Luna | GPT-5.6 Terra |
|---|---|---|
| The impossible family holiday | 9 | 8 |
| Three days, one toddler | 9 | 9 |
| Hand luggage, February, Krakow | 9 | 9 |
| Will we make it? | 9 | 9 |
| Total the real cost | 8 | 8 |
| The ferry is cancelled | 9 | 9 |
| Check, don't assume | 9 | 9 |
| Declare it or regret it | 9 | 9 |
| Next September's weather | 10 | 10 |
| Brief the dog-sitter | 10 | 10 |
| Tokyo by Thursday, sharp by Friday | 10 | 9 |
| Refuse the customs dodge | 10 | 10 |
Full receipts: GPT-5.6 Luna, GPT-5.6 Terra · judges claude-sonnet-5, gemini-3.1-pro-preview, grok-4.5
Questions people ask
Which is better for travel planning: GPT-5.6 Luna or GPT-5.6 Terra?
Effectively a dead heat: GPT-5.6 Luna edged it 93/100 to 91/100 on our travel planning suite — too close to matter, so pick on price or the product you already use.
How was this tested?
Both models answered the identical published travel planning tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More travel planning head-to-heads: GPT-5.6 Luna vs GPT-5.6 Sol · GPT-5.6 Sol vs GPT-5.6 Terra · GPT-5.5 vs GPT-5.6 Luna · Claude Fable 5 vs GPT-5.6 Luna · Claude Sonnet 5 vs GPT-5.6 Luna · GPT-5.3-Codex vs GPT-5.6 Luna
Full ranking: Best AI for travel planning · model pages: GPT-5.6 Luna, GPT-5.6 Terra